Population, breeding and conservation of Bengal monitor, Varanus Bengalensis in Bangladesh

Abstract

The study was conducted on, “Population, Breeding and Conservation of Bengal monitor, Varanus bengalensis in Bangladesh” from May 2011 to November 2014 at (1) Hazratpur and Rasulpur village, Hazratpur Union Parishad, Mithapukur, Rangpur (HU, MR); (2) Jahangirnagar University Campus and its adjacent area, Pathalia Union Parishad, Savar, Dhaka (JUC); (3) Jamuna Resort, Durgapur Union Parishad, Kalihati, Tangail (JR, T); (4) Dhaka Zoo and National Botanical Garden Mirpur Model Thana, Mirpur Dhaka (DZ & NBG); (5) Kaltapara and Bostall Village, Jampur Union Parishad, Sonargaon, Narayangonj (SN); (6) Ghorashal Power Plant, Ghorashal Municipality, Palash, Narshingdi (GPP, N) and (7) Animal Garden, Dhaka University (AG, DU). The estimated highest population density (34.5/ km2) was found in Durgapur Union, Khalihati, Tangail and the lowest (3.41 km2) was found in Mirpur Model Thana, Mirpur, Dhaka. Among eleven categories of habitats, the highest percentage of population was noted in garbage (20.1%) followed by drain (15.5%), banks of ponds and lakes (10.8%), cultivated field (9.3%), bamboo shoots and bushes (9.1%), marshland (8.6%), open space (7.5%), underground space (7.2%), sloping ground (5.5%), on the trees (5.1%) and old graveyards (1.3%). The breeding season started in July to September and ended in March-April. The nest building period was from September to October. The Bengal monitors preferred to build their active nests in termite mounds. Diameter, circumference, depth and height from the ground of the active nests were 33.6±2.9 cm, 105.6±9.2 cm, 23.2±1.1 cm and 28.1±2.7 cm respectively. The mean clutch size was 24.6±7.11 (n = 182). The length, width, girth, weight and volume of the eggs were 5.93±0.19 cm, 3.95±0.22 cm, 12.6±0.52 cm, 41.5±1.7 g and 51.4±1.8 cm3 respectively Morning and afternoon temperature of the active nests were 18.5±4.90C and 25.9±5.30C respectively. The morning and afternoon humidity was 90.8±4.0 % and 54.1±7.7 % respectively. The incubation period was 194.8±1.79 days. The length and weight of hatchlings were 23.8±0.69 cm and 17.9±1.03 g. at the time of hatching respectively. In the of sixth, twelfth, eighteenth, twenty fourth and twenty seventh month, the length and weight were 64.4±3.9 cm, 320±61.9 g ; 93.8±5.9 cm, 927.5±154.2 g ;105.9±6.6 cm, 1651.9±282.8g ; 112.9±9.2 cm, 2302.5±427.3 g and 115.3±9.8 cm, 2632.7±503.9 g respectively. The hatchlings consumed 4.9%, 7.87%, 6.6%, 5.3%, 4.3% and 4.9% of food at the age of one, six , twelve, eighteen, twenty four and twenty seven month respectively in relation to the body weight . The hatchlings shaded their skins at a time rather than part by part. The survival rate of hatchlings was 68.16% in relation to the number of eggs laid. Within concentrated areas, the population density was higher (44.0 individuals/km2) in protected zones, than in the non-protected zones (13.2 individuals/km2). They acted as natural scavengers in the environment to remove the dead and decaying materials. Percentages of scavenging individuals in drains and garbage dumps were 36.7 and 63.3 respectively. Scavenging was mostly observed between 9:00 am to 11:00 am. The number of snake biting decreased when the density of Bengal lizards increased. Bengal monitors control rat population and balancing beetle and earthworm population. The reasons for the declining of the population of Bengal monitors were due to the destruction of habitats (59%), followed by destruction of nests, eggs and hatchlings (16%), killing of adults (11%), predation (8.%), road kill (4%) and effects of pesticides (2%). Through creation of awareness during the study period, it was noted that the general people changed their impression to monitors. At the start of the research, 58.4% people showed negative impression to monitors, on the other hand, at the end of the research, 94.1% people became sympathetic to monitors.